M5.6 earthquake hits near Te Anau, seismologists say no relevance to Alpine Fault, New Zealand

A moderately strong earthquake registered by the GeoNet as M5.6 at a depth of 67 km (42 miles) hit near Te Anau in South Island, New Zealand, at 22:52 UTC on April 26, 2020 (10:52 LT on April 27). The USGS is reporting it as M4.9 at a depth of 79 km (49 miles).

The epicenter was located about 40 km (25 miles) north of Te Anau town. GeoNet said nearly 3 000 people reported feeling the quake. No aftershocks were recorded, it added.

The tremor came days after the M5.0 earthquake on April 18 at the same location. 

According to GNS Science seismologist John Ristau, the two quakes were very near together, in terms of location and depth. "It is quite possible the one last week was a foreshock to today's one."

"However, the quakes are not anything to worry about. They were not large ones, [and] earthquakes are not uncommon in this area. It's the most seismically active area in the country," Ristau added.

Ristau said the two earthquakes had "no relevance to the Alpine Fault", which runs for about 600 km (370 miles) up the South Island.

The fault had ruptured four times in the last 900 years — approximately 1717, 1620, 1450, and 1100, at intervals between 100 and 300 years — each generating a tremor of about M8.0.

The last M7.5+ earthquake along the Alpine Fault was 170 years ago; studies of the faults' strain accumulation suggest that similar events are likely to occur again.

Southland district councilor Ebel Kremer said he heard the tremor before it struck. "It was a good rattle and a bit of a rumble and a bit of rock– it was a good one that's for sure."

There were no reports of any damage, he added.

A Te Anau resident named Anna Molloy said the quake lasted up to 15 seconds. Clutha-Southland MP Hamish Walker also said the quake had a sound before it hit. "I heard it coming for about 10 seconds. It lasted for a good 20 to 30 seconds."

Arrowtown resident Chris Wozniak described it as a "strong and sharp earthquake jolt," but he said it happened quickly.

Featured image credit: Google, TW/SAM